I've been developing software for about 35 years now, and have more or less been able to keep up with the times doing so.

The best software development practise, in my experience, is to plan thoroughly and execute the plan well. Understand the users' business. Understand their functional requirements. Write and review with them a detailed set of functional specifications. Elaborate the technical specs based upon the functional ones. Develop the software, carefully reviewing it with the users at each functional point. And so on.

Buzz-words like 'agile development' and 'extreme programming' come and go; our profession is no more immune to trend and fashion than any other. What works, and which stands the test of time, is what works in many other professions as well: a dedication to careful, detailed, conscientious craftsmanship.